1. Field of the Invention
The field of the invention relates generally to mechanical power transmissions, and more particularly the invention pertains to devices and methods relating to generating clamping force in certain types of said transmissions.
2. Description of the Related Art
Certain transmissions, for example some continuously or infinitely variable transmissions, often include one or more mechanisms for generating a clamping force that facilitates the transmission of torque between or among transmission components via traction or friction. Some clamping force generators are referred to as axial force generators (AFGs) because, typically, the clamping force produced by the AFGs resolves (or must be reacted) along a main or longitudinal axis of a transmission. Hence, as used here, references to clamping force generation or clamping force generators will be understood as including axial force generation or AFGs.
One known method of generating clamping force is to place rollers between a set of load cams (or load ramps) and a reacting surface, such as for example another set of load cams or a flat driven or driving surface. As the relative motion between the opposing surfaces drives the rollers up the ramps, the rollers act to push apart the opposing surfaces. Since the opposing surfaces are typically substantially constrained to react the pushing of the rollers, a clamping force arises in the assembly. The clamping force is then usually transmitted to tractive or frictional torque transmission components.
However, devising the proper clamping force generator for any given application can be challenging. For example, difficulties can arise in providing the adequate pre-load (or initial clamping force) necessary to avoid total traction loss and/or inefficiencies (due to lost motion, for example). Hence, there are continuing needs in the relevant technology for clamping force generating mechanisms and/or methods to provide adequate clamping force for various operating conditions of certain transmissions. The devices and methods disclosed here address at least some of these needs.